1. Field of the Invention
The present invention relates to an optical film, a liquid crystal panel, and a liquid crystal display apparatus. The present invention more specifically relates to an optical film suitable for a liquid crystal display apparatus providing a colorless neutral display in all azimuth angle directions, to a liquid crystal panel employing the optical film, and to a liquid crystal display apparatus employing the liquid crystal panel.
2. Description of the Related Art
FIG. 5A is a schematic sectional view of a typical conventional liquid crystal display apparatus, and FIG. 5B is a schematic sectional view of a liquid crystal cell to be used for the liquid crystal display apparatus. A liquid crystal display apparatus 900 is provided with: a liquid crystal cell 910; retardation plates 920 and 920′ arranged on both sides of the liquid crystal cell 910; and polarizing plates 930 and 930′ arranged on outer sides of the respective retardation plates 920 and 920′. Typically, the polarizing plates 930 and 930′ are arranged such that respective polarization axes are perpendicular to each other. The liquid crystal cell 910 includes: a pair of substrates 911 and 911′; and a liquid crystal layer 912 as a display medium arranged between the substrates. One substrate 911 is provided with: a switching element (typically, TFT) for controlling electrooptic properties of liquid crystals; and a scanning line for providing a gate signal to this switching element and a signal line for providing a source signal thereto (the element and the lines not shown). The other substrate 911′ is provided with: color layers 913R, 913G, and 913B forming a color filter; and a screen layer (black matrix layer) 914. A distance (cell gap) between the substrates 911 and 911′ is controlled by a spacer (not shown).
The retardation plates are used for optical compensation of the liquid crystal display apparatus. In order to obtain optimum optical compensation (improvement in viewing angle properties, color shift, and contrast, for example), various attempts have been made in optimization of optical properties of the retardation plates and/or arrangement of the retardation plates in the liquid crystal display apparatus. As shown in FIG. 5A, the retardation plates are conventionally each arranged between the liquid crystal cell 910, and the polarizing plates 930 or 930′ (see JP 11-95208A, for example).
Further improvement in screen evenness and in display quality has been demanded for a recent high-resolution and high-performance liquid crystal display apparatus. However, the conventional liquid crystal display apparatus hardly develops a colorless neutral display in all azimuth angle directions. Further, with development of a small and portable liquid crystal display apparatus, a demand for reduction in thickness of the liquid crystal display apparatus has increased.